Grid modernization activities cite resilience (sometimes called resiliency) as a key electric power grid characteristic to be improved or maximized, and so it is crucial for the development of resilient grid architectures that the concept of grid resilience be clear and quantifiable. However, attempts to define and quantify a concept of resilience for electric power grids have mostly relied upon ad hoc definitions that do not have much underlying rigor and are often closely tied to reliability, sometimes only differing in terms of scale and frequency of events. While grid reliability would seem to have strong definition given the IEEE 1366 standard, grid resilience is a term that is less clear.